Indicator for telephony transmitters



April 28, 1931. MUTH 1,802,734

INDICATOR FOR TELEPHONY TRANSMITTERS Filed May 2, 1927 W WWWWWHMBW CONDENSER TELEPHONE IQNVENTOVR H/m's var/l BY) man A ORNEY Iatented Apr. 28, 1931 UNITED sTATEsrAr E m 50mm 1' HANS MUTH, or BERLIN, GERMANY, ASSIGNOR 'IO ensnnnsoiiarr rim nRAH'rLosE TELEGRAPHIE M. B. 11., or BERLIN, GERMANY, 'A CORPO AT ON OF ZGERMAHY;

INDICATOR r03 TELEPHONY rnn vsmrr'rnns- Application filed May 2, 1927, Serial No.'"188,204, and *in 'Germany'may 5, 1926.

A check-up of the oscillations sent out by transmitters, is necessary to ascertain whether the radio frequency oscillations have been sufiiciently modulated by the tonal 5 frequencies and also to detect any distortion caused by the modulation of the tones to be transmitted.

The arrangements heretofore used consist either of a receiver outfit comprising a rectifier circuit brought to act upon indicator device, for instance an electro-magnetic telephone, or else a luminous tube was connected directly in the sending circuit in parallel with a condenser, said tube being used to observe and ascertain the control action.

The method first mentioned involved the drawback that the operation of the apparatus became less simple since in such cases where the control device was used in the direct neighborhood of the transmitter apparatus, overloading of the rectifier circuit of the receiver apparatus was liable to happen on account of unduly large energy resulting in distortion of the tuned frequency received in the telephone, so that observation in the telephone might easily lead to wrong conclusions respecting the modulation of the transmitter, the fault really residing in the receiving apparatus.

The second method comprising the luminous indicator tube, to be sure, allows of accurate observation and ascertainin whether modulation is proper, but failed to furnish clues as to the purity of the sound.

Briefly the primary object of this invention is to provide an arrangement whereby a condenser telephone is coupled directly to a transmitter so that the oscillations sent out may be readily and accurately checked as to modulation and tone quality.

Other advantages will become apparent from the specification when read in conjunction with the annexed drawings on which G is the generator, I the high frequency chokes, V is the three element tube, C is the blocking condenser, T is the coil in the oscillating circuit, said coil being common to the input and output circuits of the three element tube, T is the antenna circuit coupled to the oscillating circuitand lis the-icon'denser telephone.

N o modulation system has been shown in the drawings as any system may be used as for instance, the constant voltage system in which a modulator tube is connected in parallel with the generator and the three element tube in the oscillating circuit.

In accordance with the present invention the condenser telephone is coupled directly to the plate circuit of a transmitter. The condenser telephone does not need a separate rectifier circuit as the vibrations of the diaphragm of such a telephone depends upon the square of the applied potentials. so that the rectifier effect, as it were, is automatically produced in the telephone circuit itself. The modulated radio frequency oscillation Which, as is well known, consists of a carrier frequency and the side bands are consequently demodulated in the circuit of the condenser telephone itself. An added advantage of this arrangement is that since high potentials are required for the actuation of a condenser telephone the condenser telephone circuit may be directly connected with the tube transmitter circuit. The coupling between the condenser telephone and the oscillating circuit may be either inductive or capacitive or direct, as indicated in the drawings. It will be noted that the condenser telephone is also coupled to the antenna circuit.

Although for the purpose of clearly disclosing my invention, I have described a, transmitting system and control device therefor, it is to be understood that I do not limit myself to said system and device as many modifications may be made without departing I claim:

1. In a high frequency signalling system a transmitter tube having a tuned output circuit comprising inductive and capacitive branches arranged in parallel, a load cirfrom the spirit of myinvention.

cuit coupled to said inductive'branch and a condenser receiving device coupled directly to a portion of said inductive branch.

2. In a high frequency system, a transmltter tube having plate, grid and filament electrodes, an energy source connected between said plate and filament electrodes a tuned circuit comprising inductive and capacitive branches in parallel connected 5 between said plate and grid electrodes means for connecting said filament to a point of said inductive branch and an acoustic condenser device connected across a portion of saidinductive branch.

1 3.'In a signalling system, a transmitter tube having a tuned output circuit compris ing inductive and capacitive branches arranged in parallel an antenna circuit coupled to one of said branches and a 0011-,

denser receiver coupled to said antenna circuit;

HANS -MUTH. 

